there are many different types. go get yourself some super oxy or any food grade 35% hydrogen peroxide aqueios solution (did i spell that right?) at any hydro shop, should be very easy to find, and mix MAXIMUM 1.5 ml per gallon and DONT use it for first to weeks. its good for your plants and i do recommend using it as ive had no problems at all but i use 1ml per gallon. ALWAYS ADD TO WATER FIRST, STIR, LET SIT 20 MINUTES, then add your nutes. hope that helps.